The present invention relates to the vulcanization of blends of thermoplastic elastomers, such as poly(etherimide ester) copolymers, or poly(ether-ester-amide) block copolymers with epoxy functionalize EPDM rubber. More particularly, the present invention relates to the melt extrusion of thermoplastic blends having an effective amount of a cross-linking agent, such as an organodiamine, and a compatibilized blend of an epoxy functionalized ethylene-propylene-polyene terpolymer (EPDM rubber) and a polyetherimide ester copolymer, or a poly(ether-ester-amide) block copolymer.
Prior to the present invention, thermoplastic elastomers, such as shown by McCready and McCready et al, U.S. Pat. Nos. 4,556,705 and 4,714,754 incorporated herein by reference, which are random poly(etherimide ester)s, were developed to provide materials which could be processed as thermoplastics and yet have the ability to retract forcibly from a large deformation. In addition, ATOCHEM of Courbevoie, France developed PEBAX resins, as shown by U.S. Pat. No. 4,230,838 which are thermoplastic elastomers in the form of poly(ether-ester-amide) block copolymers.
Although random poly(etherimide ester) copolymers, or poly(ether-ester-amide)s of the prior art are marketed as thermoplastic elastomers, new methods for improving the elastic recovery % of these materials are constantly being investigated. In addition, efforts are also directed to improving the ability of these polyether copolymers to resist deterioration of physical properties due to environmental effects such as, elevated temperatures and weathering.
The automotive industry is constantly seeking materials having enhanced % elastic recovery for applications such as CV boots in front wheel drive vehicles. In addition, these materials must be able to resist deterioration due to exposure to constant heat and weathering as determined by ASTM test D573.
A convenient procedure to determine elastic recovery % is to initially calculate the Tensile set % which can be measured on ASTM D638 type I, large Tensile bars pulled on a screw driven Instron testing machine at room temperature.
The Tensile set % can be measured at room temperature according to ASTM D638 section 11.2, and pulled at a rate of 20"/min. The Tensile set % can be calculated as follows: ##EQU1##
L.sub.after =length between the gauge marks after the specimen has been removed from the grips and allowed to relax for 10 minutes.
L.sub.original is the original length between gauge marks on the specimen (in this case 2.5 inches).
L.sub.before is the length between the gauge marks when the specimen is in the grips and pulled to fill (100 to 200%) extension.
After the Tensile set % is calculated, the elastic recovery % can be determined by substracting the Tensile set % from 100%.